At the Salk Institute, scientists have found that mild, controlled stress applied to the mitochondria of mouse embryos confers lasting protection to the adult heart — a discovery that reframes cellular adversity not as harm to be eliminated, but as a signal the body uses to prepare for future challenge. The protective messenger turns out to be citrate, a molecule that carries the memory of early stress into the genome itself through epigenetic change. This work arrives as a quiet rebuke to decades of antioxidant marketing, suggesting that the body's relationship with stress is conditional and